The oxidative damage theory of aging proposes that oxygen free radicals are responsible for the cellular changes associated with aging The majority of reactive oxygen species (ROS) are produced in the mitochondria as a byproduct of mitochondrial energy production To test this theory in mammals, Drs George Martin and Peter Rabinovitch have created a transgenic mouse model overexpressing catalase, an enzyme that prevents the formation of oxygen free radicals from hydrogen peroxide Using a beta actin promoter, the catalase was expressed chiefly in muscle and heart Targeting the catalase to mitochondria (by addition of a mitochondrial localization signal- mCAT), but not to nuclei or peroxisomes, results in a 20% increase in average lifespan and a reduction in cardiac pathology during aging (ms in preparation) This is the first genetic model in mammals to demonstrate the link between mitochondrial oxidative stress and aging The proposed experiments will investigate the molecular connections between reduced mitochondrial oxygen free radical formation and reduced cardiac pathology in this aging model We hope to establish a clear mechanism for this effect and to uncover potentially novel intracellular mediators of aging First, the response of cultured cardiac myocytes to cellular stressors that are believed to act through formation of mitochondrial oxidative stress will be analyzed to confirm at a cellular level that the overexpression of mCAT reduces intracellular signaling associated with oxidative stress Next, mitochondrial energy turnover will be analyzed and determine whether the increase in lifespan is correlated with a reduction in age-related decline of mitochondrial function Thirdly, cDNA microarrays will be used to determine the profile of age-related gene expression changes in cultured cardiac myocytes from mCAT vs. control mice These experiments will provide novel insight into the intracellular changes that correlate the overexpression of catalase in mitochondria with life extension and reduction of cardiac pathology. [unreadable] [unreadable]